Variable magnet



A. K. BEY

VARIABLE MAGNET Dec. 14, 1965 Filed May 11, 1962 INV EN TOR.

United States Patent 3,2233% VARIABLE MAGNET Ahmet K. Bey, Chicago,lll., assignor to Frances Budreck, Chicago, ill. Filed May 11, 1962,Ser. No. 194,026 3 Claims. (Cl. 317159) The present invention relates tovariable magnets. Particularly it relates to magnetic apparatus adaptedto adjust their ranges of magnetic intensity gradually between fullstrength and zero. Specifically, the invention relates to variablemagnets in which the magnetic fields can be adjusted in intensitybetween zero and maximum strength without the use of electrical energy.

In designing various apparatus, the need often arises for a magneticapparatus which is capable of providing a magnetic field of variableintensity. For example, lifting mechanisms which employ a magneticfield, normally require that the apparatus providing the magnetic fieldbe controllable whereby magnetic materials can be either picked up orreleased. Similarly, in various magnetic latching apparatus, as the typeused on refrigerator doors, it is desirable that the intensity of themagnetic field be controllable.

In addition to the types of apparatus indicated above, wherein themagnetic field is essentially either on or off, there exists a need fora magnetic means capable of providing a magnetic field which may becontinuously varied in intensity over a range between the on and offlimits. An exemplary use of an apparatus which is capable of providing avariable-intensity magnetic field is in controlling or focusing anelectron beam as utilized in electronic systems.

In the past, electromagnets have been widely used to providevariable-intensity magnetic fields. That is, electromagnets, consistingof a coil of conductive wire wound upon a core of iron, provide amagnetic field which varies in accordance with the electrical currentpassed through the coil. As a result, the intensity of the magneticfield may be controlled by varying the magnitude of the electricalcurrent passing through the coil. While electrom-agnets have wideapplication, these magnets are generally expensive to manufacture anddesign. Furthermore, electromagnets must be supplied with electricalenergy during operation, and are generally quite large relative to themaximum intensity of the magnetic field provided. A need exists for aneconomical variable magnetic means of small physical size which iscapable of producing a large magnetic intensity relative to its size.

One of the problems existent in prior art devices of the class describedhereinafter has been that a certain amount of leakage of magnetic energyis present at the non-magnetic gaps when the devices are in off ornonmagnetic positions. It would appear, therefore, that such devices,although entirely useful in lifting and latching, are not best suitedfor use in connection with all sensitive electrical equipment because ofpossible interference resulting from the magnetic leakage. It isapparent that a need exists for a variable magnet which does not rely onelectrical energy in which there is no leakage when the magnet is in theoff position.

The present invention, in its more general form, comprises a permanentmagnet, pole pieces which are secured on opposite sides of suchpermanent magnet, and another permanent magnet rotatable within saidfirst magnet, whereby a magnetic field is provided in the nonmagneticgap between the pole pieces which can be adjusted in intensity to varyover a range from maximum intensity to zero upon relative rotation ofthe permanent magnets through 180 degrees.

It is, therefore, an object of the invention to provide an improvedvariable magnet.

Another object of the invention is to provide a variable magneticapparatus which may be economically designed and manufactured.

A further object of the invention is to provide a variable magneticmeans which does not require a supply of electrical energy.

A still further object of the invention is to provide a variable :magnetwhich may be embodied in a physical structure of relatively small size.

Still another object of the invention is to provide, in a variablemagnet, which does not require a supply of electrical energy, a magneticfield which can be completely cut off.

Other and further objects and advantages of the invention will becomeapparent from the following description and appended claims, referencebeing had to the accompanying drawings, and the numerals of referencethereon.

On the drawings:

FIG. 1 is an exploded view, in perspective, of one embodiment of theinvention.

FIG. 2 is a longitudinal sectional view of the embodiment, taken on theline 22 of FIG. 4 and looking in the direction of the arrows.

FIG. 3 is a longitudinal sectional view of the embodiment, taken on theline 3-3 of FIG. 5 and looking in the direction of the arrows.

FIG. 4 is an end view of the device as seen from the bottom of FIG. 2.

FIG. 5 is an end view of the device as seen from the bottom of FIG. 3.

Referring now more particularly to the drawings, the illustrated form ofthe distinctive variable magnet or magnetic apparatus comprises a solidpermanently magnetized core 10 fabricated from preferably ferrite orother suitable materials, having high retentivity. The exterior form ispreferably cylindrical to permit relative rotation of the core 10, for areason that will hereinafter become apparent. The core 10 is magnetizedtransversely to the axis of rotation of the cylindrical form of saidcore, as illustrated in FIGS. 2, 3, 4, and 5. I have designated thepolarity of the core 10, and of the sleeve or cylinder 11, which willhereinafter be described, by the letters N and S to designate,respectively, north and south.

A second permanent magnet is provided. The second permanent magnet maybe fabricated from ferrite or other magnetic materials having highretentivity. The form of the second magnet is preferably cylindrical toprovide a sleeve 11 for disposition about the magnet 10, in a mannerthat will permit relative rotation of the core 10 and the sleeve 11. Thesleeve 11 is permanently magnetized so that the opposite poles aredisposed transversely of the axis of rotation on which the form of thesleeve is generated. As previously indicated, the north and south polesare designated by appropriate letters in the drawings.

The internal diameter of the cylinder 11 is slightly larger than theexternal diameter of the core 10, whereby when the two permanent magnetsare assembled, as illustrated in the drawings, a slight non-magnetic gapis provided between the exterior surface of the core 10 and the interiorsurface of the sleeve 11 which permits the parts to be relativelyrotated with respect to each other. It will be appreciated, by havingreference to the drawings, that magnetization of the core 10 and thesleeve 11 provides, in each thereof, a north polarity throughout theone-half of the contiguous mass of each, and a south polarity throughoutthe remaining contiguous mass, with the opposite (polarities arrangeddiametrically, rather than axially.

A curved pole plate 12, the interior radius of curvature of which issubstantially the same as the radius of curvature of the exterior ofsleeve 11, is rigidly secured to the sleeve 11 by suitable means, suchas synthetic resin or the like, well known to those skilled in the art.The pole plate 12 is fabricated from a magnetizable material, such assteel or other ferrous material; and in the device illustrated, poleplate 12 is centeredvon the surface of the sleeve 11 within the northmagnetic field, with the center of said .pole plate 12 disposed in adiametrically opposite position from a pole plate 13.

The pole plate 13 is preferably substantially in the same form as thepole plate 12 and preferably fabricated in a like manner therewith. Itis secured on the surface of the sleeve 11 by any suitable means, suchas a synthetic resin or the like, well known to those skilled in theart. The longitudinal axis of the interior surface of pole plate 13 isdisposed along a line on the surface of the sleeve 11, in which there isthe strongest south polarity. This arrangement, of course, centers thepole plate 13 in the south magnetic field, and places pole plates 12 and13 in diametrically opposite disposition. Accordingly, non-magnetic gapsareiprovided between the sides of the pole plates 12 and 13 in thespaces designated by the numerals 14 and 15, in FIGS. 4 and 5..

When the core 10, the sleeve 11 and the pole plates 12 and 13 areassembled as illustrated in FIGS. 2, 3, 4 and 5, a variable magnet ormagnetic apparatus is provided. When the position of the component is asillustrated in FIGS. 2, and 4, the magnet is referred to as being On.That is, when the north magnetic area of the surface of core is directlyunder or is coincident with the north magnetic area of the inner surfaceof the sleeve 11, the south areas of the core 10 and of the sleeve 11will be similarly disposed with respectto each other, to provide themaximum north and south magnetic fields, as illustrated in FIG. 2. Bygradual relative rotation of the core 10 with respect to the sleeve 11,from the On position, the magnetic fields are diminished until, at 180degree rotation from FIG. 2, the magnet is Off, as illustrated in FIG.3, because the components are in a theoretic position of neutralization.The On and Off positions of the magnet are labeled on the drawings.

While the device described to this point is suitable for holding orlatching purposes, the fact is that, even in the Off position, there isa slight magnetic leakage which would render the device or apparatusunsuitable for use with certain electrically actuated componentsunderstood by those skilled in the art. To completely stop all themagnetic leakage and achieve the effect theoretically available in FIG.3, I provide a magnetic leakage stopper 16. The stopper 16 in theembodiment illustrated is discor plate-like in shape and is fabricatedfrom a magnetizable material, such as soft iron or other ferrousmaterial, having a low magnetic reluctance.

The diameter of the disc or plate 16 is sufliciently large to bridge thegap formed between the core 10 and the sleeve 11, as illustrated inFIGS. 2 and 3, to thereby short out the magnetic leakage which occurswhen the components of the instant device are in the positionsillustrated in FIGS. 3 and 5. However, it will be appreciated that thestopper 16 must be free from contact with both of the pole plates 12 and13; and to that end, in the instant embodiment, the diameter of thestopper 16 is smaller than the external diameter of the cylinder orsleeve 11. In practice, the leakage stopper 16 is secured to the top ofthe sleeve 11 by means, such as a synthetic resin, well known to thoseskilled in the art.

For greatest effect, in the variable magnet herein described, I havefound that it is preferable if the mass of the core 10 is greater thanthe mass of the sleeve or cylinder 11. Preferably, the mass of the core10 should even be greater than the combined mass of the sleeve 11 andthe pole plates 12 and 13.

It will be appreciated that between the On and Off positions shown,respectively, in FIGS. 2 and 3, a magnetic field of any selectedintensity is available by suitable relative positioning of the core 10and the sleeve 11.

As many changes or substitutions could be made in the above describedconstruction, and as many apparently Widely different embodiments of theinvention within the scope of the claims could be constructed withoutdeparting from the scope and spirit thereof, it is intended that allmatter contained in the accompanying specification shall be interpretedas being illustrative and not in a limiting sense.

I claim:

1. A variable magnetic device comprising a permanently magnetized sleevehaving its poles located on opposite sides of the longitudinal axisthereof, a permanently magnetized core within said sleeve having itspoles located on opposite sides of its longitudinal axis, a pole pieceoverlying and affixed to the south pole of the sleeve and another polepiece overlying and affixed to the north pole of the sleeve, each ofsaid pole pieces extending beyond one end of the sleeve, said core andsleeve being relatively rotatable and said pole pieces being rotatablewith the sleeve whereby the intensity of the magnetic field of thedevice may be selectively varied over a Wide range by modifying therelative disposition of the poles of the core and the poles of thesleeve.

2. The magnetic device of claim 1 including a disc of magnetizablematerial overlying the ends of the core and sleeve to arrest magneticleakage therebetween with said disc being secured to the end of thesleeve and spaced from the end of the core.

3. A variable magnetic device comprising a permanently magnetized sleevehaving its poles located on opposite sides of the longitudinal axisthereof, a permanently magnetized core within said sleeve having itspoles located on opposite sides of its longitudinal axis, a pole pieceoverlying and aflixed to the south pole of the sleeve and another polepiece overlying and affixed to the north pole of the sleeve, said coreand sleeve being relatively rotatable and said pole pieces beingrotatable with the sleeve whereby the intensity of the magnetic field ofthe device may be selectively varied over a wide range by modifying therelative disposition of the poles of the core and the poles of thesleeve.

References Cited by the Examiner UNITED STATES PATENTS 2,268,011 12/1941Beechlyn 317-459 2,287,286 6/1942 Bing et a1 317l59 2,471,067 5/1949Hitchcock 317l59 2,722,617 11/1955 Cluwen et a1. 317201 X 2,793,5525/1957 Clark 317-159 X 2,972,485 2/1961 Ferchland 317-459 FOREIGNPATENTS 23,156 4/1949 Finland. 881,702 7/1953 Germany.

JOHN F. BURNS, Primary Examiner.

JOHN P. WILDMAN, LARAMIE E. ASKIN,

Examiners.

3. A VARIABLE MAGNETIC DEVICE COMPRISING A PERMANENTLY MAGNETIZED SLEEVEHAVING ITS POLES LOCATED ON OPPOSITE SIDES OF THE LONGITUDINAL AXISTHEREOF, A PERMANENTLY MAGNETIZED CORE WITHIN SAID SLEEVE HAVING ITSPOLES LOCATED ON OPPOSITE SIDES OF ITS LONGITUDINAL AXIS, A POLE PIECEOVERLYING AND AFFIXED TO THE SOUTH POLE OF THE SLEEVE AND ANOTHER POLEPIECE OVERLYING AND AFFIXED TO THE NORTH POLE OF THE SLEEVE, SAID COREAND SLEEVE BEING RELATIVELY ROTATABLE AND SAID POLE PIECES BEINGROTATABLE WITH THE SLEEVE WHEREBY THE INTENSITY OF THE MAGNETIC FIELD OFTHE DEVICE MAY BE SELECTIVELY VARIED OVER A WIDE RANGE BY MODIFYING THERELATIVE DISPOSITION OF THE POLES OF THE CORE AND THE POLES OF THESLEEVE.